Heat the chili on the stovetop in a large saucepan. In a medium saucepan, bring 4 cups of water to a boil. Add the elbow macaroni and cook over medium-high heat until al dente. Drain and add pasta back to the saucepan. Add the cheese and butter and stir until melted.
Add the mac and cheese to the chili and stir. Ladle into serving bowls immediately and top with sour cream, if desired.
Notes
Stir 1/2 cup tomato sauce or diced tomatoes to the chili for an extra saucy chili.
Add chopped green pepper (bell or jalapeno) for an extra crunch.
If you need to bump up the flavor in the chili, consider adding a touch of chili powder, beef broth or red kidney beans.